Means and method for regulating the fluid content of capillary instruments



p 1936- H. ENGELHARDT MEANS AND METHOD FOR REGULATING THE FLUID CONTENTCAPILLARY INSTRUMENTS Filed Oct. 17, 1952 I] v 1.x c v 1 on HUG oENGELPMRD T gum: Mg

Patented Sept. 22, 1936 UNITED STATES PATENT OFFICE MEANS AND METHOD FORREGULATING THE FLUID CONTENT OF CAPILLARY 1N- STRUMENTS Hugo Engelhardt,Philadelphia,

Precision Thermometer and Pa., assignor to Instrument Co.,

Claims.

My invention is designed to provide improved means and method forregulating the fluid content of the bore and bulb of a temperaturesensitive instrument so that such instrument may be readily adjusted orset with greater accuracy.

In accordance with my invention the fluid con tent of the bore isadjusted by contracting the contents of the bulb forming a supplyreservoir for the bore and thereby creating a vacuum in the bore whilethe instrument is disposed in an upright position with the top of thebore sealed by an auxiliary pool of similar fluid positioned above thebore and from which fluid is drawn into the bore by the conjoint actionof the Vacuum in the bore and the weight or gravity acting on thesuperimposed sealing pool.

The communication between the chamber containing the sealing pool andthe bore is preferably so constricted as to prevent the initiation ofdownward flow into the bore unless the action of the vacuum therein isaugmented by the weight of a substantial body of fluid in such chamberabove the bore. Hence by displacing all or the bulk of the sealing poolfrom its chamber above the bore, the instrument may be cooled withoutcausing flow of additional fluid into the bore, or the Whole or the bulkof the sealing pool may be held in the sealing chamber above the borewithout initiating flow into the bore until the instrument is cooled.

When the bore has been filled by the joint action of suction and gravityto a level above the content desired and preferably to its top, theauxiliary pool is displaced from its sealing position in the chamberabove the bore. The excess fluid contained in the bore is then expelledfrom the upper end of the bore by expanding the contents of the bulb andbore to such extent that when the fluid content is contracted to adesired degree it will have a level or volume desired under giventemperature conditions. The expelled liquid is insufiicient in weight toforce it past the constriction back into the bore when the shrinkage offluid therein by cooling again creates a vacuum, and such expelled fluidmay be displaced from the top of the bore and added to the auxiliarypool for future use.

My improvements are particularly applicable to thermostatic devicescontrolling circuits for regulating and maintaining temperatures ofcrystals used in the transmission of radio waves where a very slightvariation in the temperature of the crystal results in a substantialvariation in the wave lengths transmitted.

In the application of my improvements to such devices, conducting wires,preferably of platinum connected in a circuit, may be embedded in aglass tube so as to pierce the wall of a capillary bore extendinglongitudinally through a portion of the tube and communicating at itslower end with a bulb forming a main reservoir for a conducting liquidsensitive to temperature changes, as, for instance, mercury. The hollowupper end of the tube is of substantially greater caliber than thecapillary bore and may have a portion thereof bent over to leave asealing chamber immediately above the capillary bore and form a chamberbeside the sealing chamber and providing an auxiliary reservoir intowhich a pool of fluid may be readily shifted from the sealing chamber orvice versa.

Communication between the sealing chamber and the bore is controlled bya glass rod anchored to the wall of the sealing chamber and having itsdepending end projecting into the top of the bore so as to constrict thepassage therethrough sufficiently to interrupt and prevent continuousflow of a thermostatic liquid unless such thermostatic liquid has asubstantial head and is subjected to an unbalanced pressure in additionto its weight.

The characteristic features and advantages of my improvements willfurther appear from the following description and the accompanyingillustration of a preferred embodiment thereof.

In the drawing, Fig. 1 is an elevation of a thermostatic deviceembodying my improvements; Fig. 2 is a longitudinal sectional viewthereof, and Fig. 3 is an enlarged longitudinal sectional view of theupper end of the instrument shown in Figs. 1 and 2 showing globules ofmercury passing down the constricted section of the bore.

In the illustrative embodiment of my invention illustrated in thedrawing, a glass rod I has at the bottom thereof a bulb 2 communicatingat its top with a capillary bore 3 having a contraction chamber 4intermediate the ends thereof to avoid separation of the mercury columnin the capillary bore should the instrument be suddenly subjected toexcessive cold. The hollow upper end 5 of the glass rod has a calibersimilar to that of the bulb 2 and provides a spillway or sealing chamber5 and is bent to substantially V-shape to form an auxiliary reservoir 1in the depending leg. A glass rod 8 is fused to the inner wall of thechamber 6 and has a depending end 9 disposed within and almost closingthe top of the bore 3. A pair of platinum wires I0 and l I are sealed inthe wall of the tube I with their inner ends piercing the wall of thecapillary bore at spaced points above the contraction chamber 4. Theinstrument contains suflicient mercury l2 to fill the bulb 2, thecontraction chamber 4 and the bore section between them under minimumtemperature conditions, and in addition thereto an auxiliary pool ofmercury i2 is provided which may be thrown, by flicking the instrument,into the chamber 6 or into the chamber 7. The quantity of mercury I2 isinsufiicient to flow of its own accord from the chamber 1 into thechamber 6 in the upright position of the instrument and the I chamber 6is too small to contain sufficient mercury for its head alone toinitiate flow past the rod 8 into the bore 3. The wire H enters the bore3 a distance below the top of the bore equal to the movement of themeniscus of the mercury column as a result of a pre-determinedtemperature change, say, one degree. Each of the wires l6 and H isconnected with a conducting ring [3 and M which have connected therewithconductors I5 and I6 of a circuit containing temperature regulatinginstrumentalities, such as heating coils, not shown.

When it is desired to set the instrument so that it will operate toclose the circuit containing the wires l5 and 6 at a temperature belowthat for which the instrument was previously set, it is necessary toincrease the mercury content of the bore 3 fromthe auxiliary pool l2. Toefiect this, the auxiliary pool i2 is shifted from the chamber 1 (Fig.2) into the chamber 6 (Fig. 3) and while the instrument is in uprightposition the bulb 2 is subjected to a temperature substantially belowthat at which it is desired that the instrument operate to close thecircuit. The cooling and contraction of the mercury in the bulb causesthe mercury column to fall and create a vacuum between the meniscus ofthe column and the bottom of the pool 12 sealing the top of the bore.The suction thus created augments the head of the pool 12' to'start flowtherefrom past the rod 8 into the bore, which may be continued until thebore is filled. The remainder of the mercury I2 is then shiftedinto thechamber 1 and the bulb 2 is immersed in a bath or oven having atemperature sufiiciently higher than the temperature at which it isdesired that the instrument close the circuit to .cause a movement ofthe meniscus oi the mercury column a distance equal to the distancebetween the wire H and the top of the bore. If, for instance, thedistance between the wire l I and the top of the bore is equal to thedistance moved by the meniscus of the mercury column upon a change ofone degree in temperatura'and it is desired that the instrument operateto close the circuit at say, fifty degrees, the bulb should be insertedin a bath or oven having a temperature of fifty-one degrees. .This willexpel from the bore, past the rod 8, all the mercury in excess of thatrequired to bring the meniscus of the column into contact with the wireH at 'fifty degrees. The mercury thus expelled into the spill chamber 6has too little volume and head to flow back past the rod 8 into the borewhen the bulb is removed from the bath or oven, and may be thrown overinto the chamber 7;

When it is desired to set the instrument to operate to close the circuitat a temperature above that for which it was previously set, it is ofcourse, unnecessary to draw any, mercury into the bore from theauxiliary pool, and the instrument'is accurately set while in an uprightposition by merely inserting its bulbinto a bath or oven having atemperature one degree above that at which it. is desired the instrumentoperate, so as to expel from the bore past therod and into the spillchamber 6 the mercury in excess of that required to bring the meniscusof the mercury column into contact with the wire I I at the tem peratureat which it is desired the instrument operate. 7

By my improvements, I have provided an instrument which will operatewithin much less than the tolerance of one-tenth of a degree permissiblein controlling the temperature of radio crystals, and which may bequickly, simply and accurately set at any of the different temperaturesrequired for difierent crystals or to produce difierent wave lengths.

Having described my invention I claim:-

1. An instrument containing a capillary bore, a bulb communicating withthe bottom of said .bore, a spillway above and communicating with saidbore, a temperature sensitive liquid in said bulb and bore and a chambercontaining an auxiliary pool of temperature sensitive liquid, means of amaterial not wetted by said liquid for ,constricting flow from saidspillway into said bore, said'pool being movable into said spillway andsealing the top of said bore in the upright position of the instrument,the maximum pressure head of the pool in the spillway being insufficientalone to force liquid downward past said constricting means.

2. An instrument comprising a tube containing a capillary bore and achamber communicating with the bottom of said bore, the upper end ofsaid tube being bent to form a plurality of in said bulb and bore, anelectrically non-cone ducting rod having a section disposed in said boreand of a material not wetted by the temperature sensitive liquid, and anauxiliary pool of temperature sensitive liquid shiftable from one to theotherof said chambers, the maximum pressure head of the auxiliary poolshiftable into the chamber above the bore being insuificient to aloneforce liquid downwardly past said rod in any position of the instrument.

3. An instrument containing a bore and a substantially U shaped endforming chambers, one

of which communicates with said bore, means constricting passage to saidlast named comp-rising a glass rod through the bore adjacent chamber,and a liquid pool movable from one taining a capillary bore and chamberscommunicating with each end of said bore, a glass rod fixed to a wall ofone of said chambers and havto the other of said chambers, the maximuming an end section depending into said bore, the

upper end of said tube being bent to substantially U form, a temperaturesensitive liquid of a character non-wetting toward glass in the chamberopposite said U end of said tube, and an auxiliary pool of temperaturesensitive liquid in the U shaped end of said tube, the maximum pressurehead of the auxiliary pool shiftable into the chamber containing the rodbeing insufiicient to alone force liquid downwardly past the rod.

5. An instrument comprising a tube containing a capillary bore, a bulbcommunicating with the bottom of said bore, a spillway above andcommunicating with the bore, the upper end of said tube being bent toform a chamber communicating with said spillway above the bottomthereof, a temperature-sensitive liquid in said tube and adapted to forma main body in said bulb and bore and an auxiliary body in said chamber,and means of a material not wetted by said liquid for constrictingcommunication between said spillway and bore and permitting passage ofliquid from said spillway to said bore only when said spillway is fullof liquid and the meniscus of the main body of liquid is below saidconstricting means.

HUGO ENGELHARDT.

